The present invention relates to a printing offset blanket, and more particularly to improvements in an offset blanket for improving the same in paper discharging properties and other printing aptitudes.
As a printing method of obtaining prints of high quality, there is conventionally widely used an offset printing method.
According to the offset printing method, there are disposed a printing cylinder for carrying ink and an offset blanket coming in rotation-contact with the printing cylinder, thereby ink supplied from the printing cylinder to the offset blanket is transferred to a print carrier such as paper or the like, thus obtaining prints.
In the offset blanket printing method, the offset blanket is required to have such printing aptitudes as high paper discharging properties, good reproduciable dot shape, excellent ink applicability to a solid printing portion and the like.
If the offset blanket is particularly poor in paper discharging properties among the printing aptitudes above, this presents problems when printing operations are carried out at a high speed or on a smooth print carrier such as coated paper: adhesion acts between the print carrier and the offset blanket, which causes trouble in that the print carrier is curled or torn; bad influence such as slurs, overlaps, misregister or the like, which causes bad yield of prints.
In this connection, it has been attempted to coarsen the surface of the offset blanket in order to improve the offset blanket in paper discharging properties.
However, it often occurs that even products of the same offset blanket having the same surface roughness (which is defined in the Japanese Industrial Standards B 0601 established in 1952 and revised in 1982 and which refers to the arithmetical average of roughnesses of portions randomly extracted from the surface of a subject) are greatly different in paper discharging properties from one another. Further, the dot shape or the ink applicability to a solid printing portion generally requires fine surface roughness, so that the coarsening of the surface for the purpose of improving the paper discharging properties cannot improve the paper discharging properties so much, but causes decay of other printing aptitudes such as dot shape, ink applicability to a solid printing portion and the like.
In other words, it is difficult to obtain the surface configuration having the desired printing aptitudes by merely coarsening the surface.
In view of the defects above, the present invention is proposed with the object of providing an offset blanket having excellent paper discharging properties.
It is another object of the present invention to provide an offset blanket capable of reconciling high paper discharging properties with good dot shape and ink applicability to a solid printing portion.